In Phase I a novel cytokine was purified homogeneity and its unequivocal N-termina sequence (27 amino acids) was obtained. Phase I application referred to this molecule as contra IL1 an inhibitor of IL1. Preliminary cell biological and immunological studies have revealed a unique set of properties. It inhibits IL1, IL2, and IL6-induced T cell proliferation at a late stage of activation. Its mode of action is cytostatic rather than cytotoxic, hence the new designation cytostatin. During Phase II the investigators plan to clone the cDNA for cytostatin using nucleotide probes designed from the novel amino acid sequence to screen a lambda qt 10 library. They plan to express the cDNA for cytostatin using bacterial, yeast, or mammalian expression systems. With the purified protein cytostatin in patients with various diseases of immune dysfunction. Finally They will use the recombinant protein to define its autoimmune and inflammatory diseases. Based on invitro studies, cytostatin has potential for the thera of various immune disorders such as organ transplantation and autoimmunity. Overproduction of cytostatin may account for some of the immunosuppression observed in AIDS and cancer patients.